The present invention relates generally to the casting arts and more particularly to a method and apparatus for automatically forming sand molds.
Sand molds are usually formed of a lower or drag section and a mating, cooperating upper or cope section. Each of the two sections have cooperating impressions formed therein by means of a model or master so that molten metal can be poured between the two sections and into the impressions and subsequently cooled in order to assume the configuration corresponding to the impressions in the opposing, cooperating sand mold sections. In the past this procedure has been carried out manually and, as such, was time consuming. Clearly, manual operations do not lend themselves to and are not suitable for present day high speed industrial requirements.
Sand mold formation machines have been developed wherein sand has been deposited in an enclosure and wherein opposing pattern plates are displaced towards one another into the enclosure in order to compact the sand. The pattern plates impart, on opposite faces of the sand, an impression corresponding to the impression in the pattern plates. After removing or retracting the pattern plates from the enclosure, ejectors are used for displacing the mold sections that have been formed in the enclosure. The ejected mold section is provided with two opposing faces which, if disposed opposite another mold section formed in the manner described, can be used for cooperatively receiving molten metal which fills the cavity defined by the opposing faces. When the molten metal is cooled, it can be removed from the mold sections and any subsequent finishing operations can be then performed. A plurality of the mold sections can be placed side by side to thereby permit the continuous pouring of molten metal into the mold sections.
One machine that is conventional and which is known in the art provides means for rapidly forming the mold by means of a bed that can be reciprocated between two positions. After the mold is formed in a first enclosure by opposing pattern plates, the bed is shifted to a second position after the pattern plates have been retracted in order to permit a first ejector to enter the first enclosure and eject the mold formed therein. While the ejector is displacing the formed mold from the first enclosure, a second mold is being formed by the pattern plates in a second enclosure. After the first mold is ejected from the first enclosure, the first ejector is retracted, together with the opposing pattern plates which have operated upon the second enclosure to form the second mold, the bed is then shifted or reciprocated in the opposite direction in order to align the second enclosure with a second ejector that is on the opposite side of the pattern plates. The second ejector enters the second enclosure and ejects the second mold which is then directed to a second station. During the ejection of the second mold, a third mold is being formed in the first enclosure and again the bed is reciprocated to the first ejector position. This procedure is repeated continuously. In order to provide a great number of sand mold portions, the sand mold portions are positioned opposite one another in two parallel, linear arrays which can be further operated upon independently.
While the prior art apparatus just described does represent a substantial improvement over manual operations, it still does exhibit several disadvantages. That is, the sand receiving enclosure cannot be readily adjusted for releasing the formed sand mold sections. Therefore, since the sand when compacted adheres to the surfaces of the enclosure, it is very difficult to eject the formed sand mold sections without causing damage thereto. Another disadvantage of the prior art machine previously described resides in the contact of the face of the ejector with portions of the impressions that have been formed in the sand. Since the weight of the mold is heavy, it is necessary for the ejector to exert large forces against the sand in the mold in which the impressions have been formed. Therefore, it is not uncommon for the ejector to damage the impression. Even where means are provided for preventing the ejector from contacting the impression area in the sand it is impossible for the ejector to exert a uniform pressure against the entire surface of the mold sections. Thus, there is a likelihood of distortions of the mold section as it is displaced by the ejector.
Still another disadvantage of the conventional prior art machine described above is the absence of provisions for rapidly replacing the patterns in order to permit the formation of mold sections having different impressions. In any production run, the mold sections will have identical patterns. However, when it is necessary to change over to another run where different impressions are required, it is very difficult with the prior art apparatus to change the pattern plates of the machine.
Another form of prior art apparatus for forming sand molds is disclosed in my issued U.S. Pat. No. 3,744,550 granted on July 10, 1973. In my issued patent there is disclosed apparatus which includes an elongated bed having adjacent and partially enclosed receptacles for alternately receiving sand. A top cover plate is used for partially further enclosing the receptacles in an alternating pattern. The top cover plate is operatively associated with the receptacles for alternately adjusting the configuration of the receptacles from the configuration for operating on the sand disposed therein to form a mold to that configuration for releasing the mold so formed therein. A pair of opposing cooperating pattern plates are shiftably supported for entering together into each of the receptacles respectively, in opposing relation, to compact the sand disposed in the receptacles. A pair of mold ejectors are also utilized for entering the receptacles alternately and for ejecting the mold formed in the receptacles. The elongated bed is capable of reciprocating in a longitudinal direction over a plurality of selected positions such that the pattern plate and the ejectors can be aligned properly opposite selected ones of the receptacles alternately in operative association with the receptacles. The ejectors utilize pressurized fluid to aid in the ejection process and the pattern plates are each provided as a group of at least two patterns that may be reciprocated vertically in order to effect a change in the type of patterns utilized.
While my issued U.S. patent represents a substantial improvement over the apparatus previously available, it has been found that still other improvements can be made.